This disclosure relates to an energy management system for a hybrid electric or electric non-railbound vehicle comprising an electrical power collector for intermittently collecting electrical power from an external power supply track during driving of the vehicle, wherein the energy management system is arranged to distribute electrical power from the electrical power collector to at least one electrical auxiliary load of the vehicle when collecting electrical power from the external power supply track. The disclosure also relates to a method for controlling operating characteristic of at least one auxiliary load of a hybrid electric or electric vehicle comprising an electrical power collector for intermittently collecting electrical power from an external power supply track during driving of the vehicle. The vehicle propulsion system and corresponding method may be implemented in many types of road and off-road vehicles, such as trucks, busses, cars, construction vehicles, and the like.
Hybrid-electric vehicles having a combustion engine and an electrical traction machine have a limited driving range and it is known for example from FR2809998 to provide the hybrid-electric vehicle with an electrical power collector for collecting electrical power from an external power supply track, thereby enabling the vehicle to be driven in a pure electric mode. This aspect consequently increases the propulsion flexibility, increases the driving range and reduces emissions. Known energy management systems for this type of vehicles are however still not fully developed and further improvements in performance and cost-saving are possible.
It is desirable to provide an improved energy management system for a hybrid electric or electric non-railbound vehicle comprising an electrical power collector for intermittently collecting electrical power from an external power supply track during driving of the vehicle.
The disclosure concerns an energy management system for a hybrid electric or electric vehicle comprising an electrical power collector for intermittently collecting electrical power from an external power supply track during driving of the vehicle, the energy management system is arranged to distribute electrical power from the electrical power collector to at least one electrical auxiliary load of the vehicle when collecting electrical power from the external power supply track.
The disclosure is characterized in that the energy management system comprises a control unit configured to control operating characteristic of the at least one auxiliary load depending on if the vehicle operates in a power collecting mode or in a non-power collecting mode.
The disclosure also concerns a method for controlling operating characteristic of at least one auxiliary load of a hybrid electric or electric vehicle comprising an electrical power collector for intermittently collecting electrical power from an external power supply track during driving of the vehicle, wherein electrical power may be distributed from the electrical power collector to the at least one electrical auxiliary load of the vehicle when collecting electrical power from the external power supply track, the method comprising the steps of                determining if the vehicle operates in a power collecting mode or in as non-power collecting mode; and        controlling operating characteristic of the at least one auxiliary load depending on if the vehicle operates in a power collecting mode or in a non-power collecting mode.        
Energy management during slide-in driving is about using the available energy in the most efficient way in order to fulfil the vehicle needs to be able to perform the propulsion and to run auxiliaries in a satisfactory way. Different energy handling strategies is possible depending on the conditions of the vehicle as well as of how the vehicle is equipped. This invention is about how to utilize the available grid energy in a more efficient way which means that you may in the long run save fuel and/or battery energy/usage.
The core of the disclosure is to control the operating characteristic of the vehicle auxiliary loads depending on whether the vehicle collects electrical power from the external grid or not. The thought behind the control strategy is that energy supplied from the power supply track can be regarded as having a lower cost per energy unit compared with energy taken from a vehicle on-board combustion engine or an on-board electrical storage system, such as batteries or super capacitors. The lower cost is partly due to the low efficiency of the conventional gasoline or diesel combustion engines, which effectively use only about 15%-20% of the fuel energy content for propulsion and powering auxiliaries. Electric drive vehicles however, due to the high efficiency of the electrical motor, typically have on-board efficiencies of around 80%. Also, by using electrical energy from the power supply track instead from the on-board battery eliminates any charge and discharge energy losses that otherwise inherently occurs when using the on-board battery.
Conventional powering an electrical propulsion system and electrical auxiliary loads using electrical power from the power supply track when available results in a first energy saving effect. This disclosure aims at further increasing the first energy saving effect by specific control the energy usage of the auxiliary devices, depending on if the vehicle operates in a power collecting mode or in a non-power collecting mode. The specific control enables improved energy efficiency. For example, based on the fact that energy from the power supply track has a lower cost, the inventive control strategy may involve using the auxiliary load relatively more when the system is connected to the external power supply track, compared with a normal usage level during driving in corresponding circumstances and without collecting power from the grid. This strategy will result in overall reduced energy consumption if the auxiliary loads are associated with some kind of energy storage capacity. If for example the auxiliary load is an electrical motor driving an air compressor unit for filling the vehicle air tanks, the relatively cheap energy from the power supply track may be excessively used in a power collecting mode for temporarily storing the relatively low-cost energy on the vehicle for later use. Important is also that the energy storage system does not exhibit a significant energy-loss at charging, storing and discharging phases, because this aspect may then consume the cost-saving effect of the disclosure. For example, temporarily lowering the temperature in a storage compartment of a refrigerator truck will generally result in an increased energy loss due to increased thermal loss through the walls of the storage compartment. Consequently, most preferably, the additional energy from the power supply track is stored and subsequently used without significantly increasing the total amount of power consumption.
The control unit may be configured to increase the total power consumption level of the at least one auxiliary load when operating the vehicle in a power collecting mode, compared with the total power consumption level of said at least one auxiliary load when operating the vehicle in corresponding circumstances in a non-power collecting mode. This control strategy delivers the desired improved energy efficiency discussed above.
The energy management system may be arranged to charge an energy storage devices associated with the at least one electrical auxiliary load of the vehicle to a predetermined maximal level when collecting electrical power from the external power supply track. Charging the energy storage device using relatively low-cost energy from the external power supply track enables storage of that low-cost energy on-board the vehicle for later use, thereby reducing the level of energy required from the on-board combustion engine, such that overall fuel-efficiency is improved.
The energy storage devices may be charged by filling an air storage tank with compressed air, filling a hydraulic accumulator with pressurised hydraulic fluid, lowering the temperature of a cargo refrigerator compartment, or by increasing or decreasing the temperature of a driver's cabin depending on the circumstances
The energy management system may comprise vehicle relative position determining means arranged to determine vehicle position in relation to power supply track availability. The vehicle relative position determining means may be relatively simple and capable of only detecting availability of the power supply track at the current position of the vehicle. A more complex vehicle relative position determining means may have capacity of also calculating the distance and/or time remaining until reaching a start point of a power supply track segment, and/or calculating the distance and/or time remaining until reaching an end point of a power supply track segment. With knowledge of the vehicle position in relation to power supply track availability more intelligent control of the electrical auxiliary loads of the vehicle is enabled.
The vehicle relative position determining means may comprise any of a global positioning system (GPS) in combination with geographical power supply track installation information, a dedicated short-range communication system (DSRC) for communication with the power track installation, or radio-frequency identification (RFID) technology or similar transmitter/responder technology for determining the availability of power supply track at present vehicle position.
The control unit may be configured to estimate a time period until the electrical power collector will start collecting electrical power based on determined vehicle position in relation to start point of power supply track availability. Thereby more intelligent control of the electrical auxiliary loads of the vehicle is enabled.
For example, the control unit may be configured to control operating characteristic of the at least one auxiliary load depending also on if the estimated time period until the electrical power collector will start collecting electrical power from the external power supply track is within a predetermined time window. In particular, the control unit may be configured to decrease the total power consumption level of the at least one auxiliary load when the estimated time period until the electrical power collector will start collecting electrical power from the external power supply track is within a predetermined time window, compared with the total power consumption level of said at least one auxiliary load when operating the vehicle in corresponding circumstances outside said predetermined time window. Thereby relatively expansive energy from the combustion engine may be replaced by relatively low-cost energy from the power supply track.
Furthermore, the control unit may be configured to estimate a time period until the power collector will disconnect from the external power supply track based on determined vehicle position in relation to end point of power supply track availability. Thereby more intelligent control of the electrical auxiliary loads of the vehicle is enabled. For example, the control unit may be arranged to, upon collecting electrical power from the external power supply track during driving of the vehicle, coordinate operation of the at least one electrical auxiliary load with the estimated time period until the power collector will disconnect from the external power supply track and the energy charge level of the associated energy storage device, for enabling the associated energy storage device to attain the predetermined maximal level at time of disconnection from the external power supply track. Thereby a maximal energy saving effect is realised.
The control unit may be arranged to prioritise supply of electrical energy from the electrical power collector to an electrical traction machine of the vehicle, and to limit the supply of electrical energy from the electrical power collector to the at least one electrical auxiliary load to prevent that a maximal permitted power transmission level of the power collector or a maximal permitted electrical load level of the power supply track is exceeded. The propulsion function of the vehicle is prioritised because propulsion generally corresponds to the largest load of the vehicle, and replacing the largest load with low-cost energy from the power supply track generally results in the largest cost savings.
The electrical auxiliary load may be formed by an electrical heating device for heating an electrical storage system, a driver's cabin, a vehicle seating, a vehicle window, a vehicle steering wheel, or a vehicle side mirror. An electrical heating device may also be considered as an energy storage device but with a relatively high energy loss rate.
The electrical auxiliary load may be formed by any of an electrical machine driving an air compressor unit/pump, an electrical machine driving as compressor unit of a vehicle air conditioning system, a vehicle electrical power take-off for operating at least one electrical load located on the vehicle or a trailer connected to the vehicle, or an electrical machine driving, a water cooling system or air cooling system of the vehicle.
The electrical auxiliary load may be formed by an electrical machine driving a hydraulic pump of a hydraulic system. The hydraulic system may comprise a hydraulic motor for propulsion of the vehicle, a hydraulic cylinder for operating an implement of the vehicle, a hydraulic cylinder for steering of an articulated vehicle, or a hydraulic accumulator for temporarily storing hydraulic energy.
The electrical power collector may be arranged to collect electrical power while being in sliding contact with an electrical conductor of the power supply track, or by inductive coupling between the electrical power collector and the power supply track.
In addition to above, the disclosure concerns a corresponding method.